Melamine Plant Gas Stream Diversion for Clogging Prevention
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Solution Overview
Problem
In melamine production plants, the absence of urea feed during transitional phases leads to challenges in scrubbing gaseous streams, causing clogging and requiring alternative methods or rapid emptying of reaction sections, as molten urea degradation and melamine precipitation occur, and the urea plant receives unscrubbed CO-free off-gases, disrupting the NH3/CO2 ratio and increasing energy consumption.
Innovation Solution
An apparatus and process that divert gaseous streams from the reaction and post-reactor to other sections within the melamine plant for scrubbing and absorption, excluding the urea scrubbing step during non-productive phases, using transfer lines and shut-off valves to route these streams to sections capable of receiving them, ensuring continuous ammonia supply and preventing clogging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If molten urea is used for scrubbing gaseous streams during transitional phases, then melamine can be recovered from the gas phase, but urea degradation occurs leading to clogging and system blockage
Solution Approach 1:
The patent extracts the harmful CO2 component from the gaseous stream by diverting it to a dedicated combustion chamber where it is burned off. This separates the problematic CO2 from the melamine-containing stream, allowing the latter to be treated without causing urea degradation and clogging that would occur with conventional scrubbing methods
Solution Approach 2:
The patent introduces an intermediary combustion chamber and heat exchanger system between the reaction section and the scrubbing section. This intermediary system pre-treats the gaseous stream by removing CO2 and recovering heat, preventing the direct contact between molten urea and CO2 that would cause degradation and clogging
2Ease of operation
If ammonia is fed to the reaction section during transitional phases, then the reaction section can be maintained and flushed, but CO-free off-gases are sent to the urea plant disrupting the NH3/CO2 ratio and increasing energy consumption
Solution Approach 1:
The patent converts the harmful CO2 that would otherwise disrupt the urea plant's NH3/CO2 ratio into a beneficial fuel source by directing it to a combustion chamber where it is burned to generate heat. This heat is then recovered via heat exchangers to preheat feed streams, turning the energy-wasting CO2 emission into a useful heat source that reduces overall energy consumption
Solution Approach 2:
The patent changes the destination and treatment of the off-gas stream by diverting CO2-rich gases to a combustion chamber instead of sending them directly to the urea plant. This parameter change in gas routing and treatment converts a harmful CO2 stream into a heat-generating fuel, thereby eliminating the disruption to the urea plant's chemical balance and reducing energy consumption
3Reliability
If rapid emptying of the reaction section is performed to avoid clogging, then operational safety is improved, but production time is lost and productivity decreases
Solution Approach 1:
The patent performs preliminary action by continuously removing CO2 through the dedicated combustion chamber during normal operation and transitional phases. This prevents the accumulation of CO2 that would lead to clogging, eliminating the need for rapid emptying operations and allowing continuous, uninterrupted production
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution allows for continuous ammonia supply to the reaction section during transitional phases, preventing clogging and reducing energy consumption by avoiding CO-free off-gas sent to the urea plant, enabling efficient scrubbing and recovery of melamine without urea recycling issues.
Implementation Method 1
a scrubbing section (L) suitable for scrubbing the gaseous stream coming from the reactor with urea
Implementation Method 2
the gaseous streams exiting from the upper portion of the reactor and post-reactor... composed of NH3, CO2 and melamine in vapour phase
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
An apparatus is described for the treatment of gaseous streams leaving the reaction section in a plant for the production of melamine together with the corresponding process.